The present invention relates to a writing apparatus and method wherein a pen supporting arm holding a pen at the tip of the arm is moved along a horizontal x-axis and a horizontal Y-axis perpendicular to each other, and the rail is swung up to swing up the arm to move up the pen from the surface of writing paper and swung down to swing down the arm to move down the pen to the surface of the paper.
In a writing apparatus and method of such kind, a pen support arm which is moved over a prescribed area of a casing frame along a horizontal x-axis and a horizontal y-axis perpendicular to each other, is repeatedly swung up and down so that a pen held by the arm is repeatedly put into and out of contact with the surface of writing paper to write a character, a figure or the like thereon.
The apparatus includes a mechanism which is for repeatedly swinging the pen support arm up and down and has a pen lifting rail supported by the casing frame and disposed under the arm so that the rail can be swung up and down into and out of contact with the bottom of the arm to swing it up and down. As for the mechanism, an unpleasant impact noise is made every time the pen lifting rail is swung up into contact with the bottom of the pen support arm. This is a problem because the noise acts to deteriorate the efficiency of work in an office or the like.
To solve the problem, it was proposed in the Japanese Utility Model Application (OPI) No. 148389/89 (the term "OPI" as used herein means an "unexamined published application") that a sound absorber is attached to the pen lifting rail. Meanwhile, the impact noise consists of not only a noise made by the collision of the rail against the arm, but also noises caused at the portion of the mechanism due to the vibration of the entire mechanism, which results from the collision. The latter noises are higher in intensity than the former. Therefore, only attaching the sound absorber to the rail does not produce an effect to reduce the impact noise well. Besides, attaching the absorber to the rail results in increasing the number of the parts of the writing apparatus, the assembly work thereof and the cost of the apparatus, and is therefore not desirable.
In addition, in a conventional writing apparatus includes a mechanism which is for repeatedly swinging the pen support arm up and down and has a pen lifting rail supported by the casing frame and disposed under the arm so that the rail can be swung up and down into and out of contact with the bottom of the arm to swing it up and down. In the mechanism, the pen lifting rail is supported in a prescribed location by the casing frame so that the rail can be swung up and down. For that reason, the distance h1 between the pen support arm 4 and the pen lifting rail 5 in the case that the pen held by the arm at the tip thereof is located nearest the frame as shown in FIG. 12(a) differs from that h2 between the arm and the rail in the case that the pen is located farthest from the frame as shown in FIG. 12(b). Therefore, the speed of the upward swinging of the rail 5 at the time of the contact thereof into the arm 4 in the former case differs from that in the latter case. As a result, the impact of the rail 5 on the arm 4 in the former case is heavier than that in the latter case. Since the arm 4 bounces as a whole when receiving the impact, the next writing action of the apparatus cannot properly be performed until the bounce disappears. If the arm 4 were swung down during the bounce in order to perform the next writing action, the pen would be vibrated up and down to have its tip come into contact with the surface of the writing paper to give ink to an unnecessary part of the surface. For that reason, the time point at which the rail swung up after the previous writing action of the apparatus is swung down to swing down the arm to move down the pen to perform the next writing action is preset depending on the time which it takes for the bounce of the arm to disappear in the latter case that the pen is located farthest from the casing frame. As a result, in the former case, the pen is not moved down until the lapse of the time although the pen can be moved down in the time. In other words, a waiting time longer than a necessary length is spent so that the efficiency of writing by the apparatus is deteriorated. This is a problem.
Further, in a conventional mechanism for moving a pen up and down in a writing apparatus of such kind, a pen lifting rail for swinging up and down a pen support arm holding the pen at the tip of the arm is disposed near the front edge of a casing frame and supported at both the ends of the rail near the right and left sides of the frame so that the rail can be swung up and down in a prescribed range to come into and out of contact with the bottom of the arm to swing it up and down to move the pen up and down. The length of the vertical movement of the pen depends on the location thereof along a horizontal y-axis or depends on whether the pen is located near or away from the casing frame. When the pen held by the arm at the tip thereof is located near the frame, the rail is swung up and down into and out of contact with the arm near the tip thereof to swing the arm up and down to move the pen up and down. When the pen is located far from the frame, the rail is swung up and down into and out of contact with the arm near the butt thereof to swing the arm up and down to move the pen up and down. Since the length of the vertical swing of the rail is always constant, the length of the vertical movement of the pen in the case that the arm holding the pen at the tip of the arm is swung up and down by the rail located near the butt of the arm is larger than that in the case that the arm is swung up and down by the rail located near the tip of the arm. In the former case, the pen bounces up and down on the surface of writing paper so as to much deteriorate the quality of writing thereon with the pen as it falls into contact with the surface of the paper. Since the length of the vertical movement of the pen is smaller in the latter case, the tip of the pen is likely to do damage such as tear to the paper if it has a projection for the pen to engage with. To proceed from a step of writing to a next step of writing, the pen support arm is once swung up, then horizontally moved, and thereafter swung down. The time which it takes to proceed from the preceding step of writing to the next step of writing depends much on the location of the pen along the y-axis. Since the preset length for the time needs to be equalized to the maximum of the time, the efficiency of writing by the apparatus is low.
Furthermore, in a conventional writing apparatus including an x-axis rail supported by a casing frame so as to be movable relative to the frame along a y-axis, and a pen support arm holding a pen at the tip of the arm and supported by the rail so as to be movable relative to the rail along a horizontal x-axis perpendicular to the y-axis, the rail needs to be precisely moved along the y-axis. In a control mechanism for the precise movement of the rail along the y-axis, the rail is secured at both the ends thereof to timing belts extending along the y-axis, and one of the belts is revolved to move the rail along the y-axis. The timing belts are engaged at both the ends thereof with toothed pulleys supported by the casing frame. Although the mechanism does not have a problem in the normal writing operation of the apparatus, the mechanism has a problem that when the pen support arm is forcibly pulled out much from the casing frame in order to attach the pen to the arm, one of the timing belts is pulled more strongly than the other if the arm is off the center line of the right-to-left width of the frame. The tooth of the timing belt pulled more strongly than the other is disengaged from one tooth of a toothed pulley and then engaged with another tooth thereof so that the position of the belt deviates from that of the other belt by one pitch to result in moving the arm on wrong tracks along the x-axis and the y-axis to make the writing operation of the apparatus improper.